1.three phase induction motor protection system
TRANSCRIPT
-
8/18/2019 1.Three Phase Induction Motor Protection System
1/122
THREE PHASE INDUCTION MOTOR PROTECTION FROM
SINGLE PHASING & OVER HEATING
A
Project Report Submitted in
partial fulfillment of the requirement for the award of degree of
BACHELOR OF ENGINEERING
In
ELECTRICAL AND ELECTRONICS ENGINEERING
By
SHAIK JUNAID 1604-12-734-014
SHAIK MOHAMMED NASER 1604-12-734-037
ALLAM SRI SAI VAJRAANG 1604-12-734-052
Under the Guidance of
Mrs. NAUSHEEN BANO
Associate Professor
Electrical Engineering Department
1
-
8/18/2019 1.Three Phase Induction Motor Protection System
2/122
Muffakham Jah College of Engineering & Technology
(Affiliated to Osmania University)
2015-2016
INDEX
TOPICS
1.Certificates
2.Acknowledgement
CHAPTER 1: INTRODUCTION
1.1 Introduction of the project
1.2 Project overview
1.3 Thesis
CHAPTER 2: EMBEDDED SYSTEMS
2.1 Introduction to embedded systems
2.2 Need of embedded systems
2.3 Explanation of embedded systems
2.4 Applications of embedded systems
CHAPTER 3: HARDWARE DESCRIPTION
2
-
8/18/2019 1.Three Phase Induction Motor Protection System
3/122
3.1 Introduction with block diagram
3.2 Microcontroller
3.3 Regulated power supply
3.4 LED indicator
3.5 Voltage sensor
3.6 Optocoupler
3.7 Relay
3.8 LCD
CHAPTER 4: SOFTWARE DESCRIPTION
4.1 Express PCB
4.2 PIC C Compiler
4.3 Proteus software
4.4 Procedural steps for compilation, simulation and dumping
CHAPTER 5: PROJECT DESCRIPTION
CHAPTER 6: ADVANTAGES, DISADVANTAGES AND APPLICATIONS
CHAPTER 7: RESULTS, CONCLUSION,FUTURE PROSPECTS
REFERENCES
3
-
8/18/2019 1.Three Phase Induction Motor Protection System
4/122
CHAPTER 1: INTRODUCTION
1.1Introduction:
The aim of this project is to construct a three phase fault
monitor and prevention system using 8-bit microcontroller. The three
phasing fault analysis to prevent faults the system automatically
resets are required for critical loads and circuits. These are required
because the normal overload protection doesn't trip on time. For large
air-conditioning compressors, irrigation pumps these are sometimes,
included.
The purpose of this project is to develop an intelligent system that
continuously monitors all the three phase voltages (High voltage AC)
and if any of these three phases is disconnected then this system
takes the preventive action. The preventive action could be
4
-
8/18/2019 1.Three Phase Induction Motor Protection System
5/122
disconnecting the power supply immediately to the load by operating
an electromagnetic relay. This system also alerts the user using visual
alerts on the LCD display module.
This system consists of three optically isolated high voltage sensors for
sensing the presence of high voltage in the respective circuits. One of
the voltage sensors is connected to phase line of the supply and the
other is connected to neutral line. A microcontroller based control
system continuously monitors the voltage in all the three phases of
the power supply circuit. In ideal conditions all the three phases gets
the same voltage. The visual indicators display the health status of all
three phases (Red, Yellow and Green). But, when any of the phases
gets disconnected then in such situations the microcontroller-based
system alerts the user using LCD module.
1.2 Project Overview:
An embedded system is a combination of software and
hardware to perform a dedicated task.Some of the main devices used
in embedded products are Microprocessors and Microcontrollers.
Microprocessors are commonly referred to as general
purpose processors as they simply accept the inputs, process it and
give the output. In contrast, a microcontroller not only accepts the
data as inputs but also manipulates it, interfaces the data with
various devices, controls the data and thus finally gives the result.
5
-
8/18/2019 1.Three Phase Induction Motor Protection System
6/122
The Microcontroller based automatic Single Phasing
Preventing System for 3-phase Industrial Motors using PIC16F72
Microcontroller is an exclusive project that can be used to design and
construct a single phasing monitor and prevention system using 8-bit
microcontroller.
The purpose of this project is to develop an intelligent system
that continuously monitors all the three phase voltages (High voltage
AC) and if any of these three phases is disconnected then this system
takes the preventive action. The preventive action could be
disconnecting the power supply immediately to the load by operating
an electromagnetic relay. This system also alerts the user using LCD
Display system.
1.3 Thesis Overview:
The thesis explains the implementation of
“ THREE PHASE INDUCTION MOTOR PROTECTION SYSTEM” using
PIC16F72 microcontroller. The organization of the thesis is explained
here with:
6
-
8/18/2019 1.Three Phase Induction Motor Protection System
7/122
Chapter 1 Presents introduction to the overall thesis and the
overview of the project. In the project overview a brief introduction of
THREE PHASE INDUCTION MOTOR PROTECTION SYSTEM” and
its applications are discussed.
Chapter 2 Presents the topic embedded systems. It explains the
about what is embedded systems, need for embedded systems,
explanation of it along with its applications.
Chapter 3 Presents the hardware description. It deals with the block
diagram of the project and explains the purpose of each block. In the
same chapter the explanation of microcontrollers, power supplies,
relay, LCD, voltage sensor, optocoupler are considered.
Chapter 4 Presents the software description. It explains the
implementation of the project using PIC C Compiler software.
Chapter 5 Presents the project description along with relay, voltage
sensor, LCD modules interfacing to microcontroller.
Chapter 6 Presents the advantages, disadvantages and applications
of the project.
Chapter 7 Presents the results, conclusion and future scope of the
project.
CHAPTER 2: EMBEDDED SYSTEMS
7
-
8/18/2019 1.Three Phase Induction Motor Protection System
8/122
2.1 Embedded Systems:
An embedded system is a computer system designed to
perform one or a few dedicated functions often with real-time
computing constraints. It is embedded as part of a complete device
often including hardware and mechanical parts. By contrast, a
general-purpose computer, such as a personal computer (PC), is
designed to be flexible and to meet a wide range of end-user needs.
Embedded systems control many devices in common use today.
Embedded systems are controlled by one or more main
processing cores that are typically either microcontrollers or digital
signal processors (DSP). The key characteristic, however, is being
dedicated to handle a particular task, which may require very
powerful processors. For example, air traffic control systems may
usefully be viewed as embedded, even though they involve mainframe
computers and dedicated regional and national networks betweenairports and radar sites. (Each radar probably includes one or more
embedded systems of its own.)
Since the embedded system is dedicated to specific tasks,
design engineers can optimize it to reduce the size and cost of the
product and increase the reliability and performance. Some embedded
systems are mass-produced, benefiting from economies of scale.
Physically embedded systems range from portable devices
such as digital watches and MP3 players, to large stationary
installations like traffic lights, factory controllers, or the systems
controlling nuclear power plants. Complexity varies from low, with a
single microcontroller chip, to very high with multiple units,
peripherals and networks mounted inside a large chassis or enclosure.
8
-
8/18/2019 1.Three Phase Induction Motor Protection System
9/122
In general, "embedded system" is not a strictly definable
term, as most systems have some element of extensibility or
programmability. For example, handheld computers share some
elements with embedded systems such as the operating systems and
microprocessors which power them, but they allow different
applications to be loaded and peripherals to be connected. Moreover,
even systems which don't expose programmability as a primary
feature generally need to support software updates. On a continuum
from "general purpose" to "embedded", large application systems will
have subcomponents at most points even if the system as a whole is
"designed to perform one or a few dedicated functions", and is thus
appropriate to call "embedded". A modern example of embedded
system is shown in fig: 2.1.
Fig 2.1:A modern example of embedded system
Labeled parts include microprocessor (4), RAM (6), flash
memory (7).Embedded systems programming is not like normal PC
programming. In many ways, programming for an embedded system is
9
-
8/18/2019 1.Three Phase Induction Motor Protection System
10/122
like programming PC 15 years ago. The hardware for the system is
usually chosen to make the device as cheap as possible. Spending an
extra dollar a unit in order to make things easier to program can cost
millions. Hiring a programmer for an extra month is cheap in
comparison. This means the programmer must make do with slow
processors and low memory, while at the same time battling a need for
efficiency not seen in most PC applications. Below is a list of issues
specific to the embedded field.
2.1.1 History:
In the earliest years of computers in the 1930–40s,
computers were sometimes dedicated to a single task, but were far too
large and expensive for most kinds of tasks performed by embedded
computers of today. Over time however, the concept ofprogrammable
controllers evolved from traditionalelectromechanical sequencers, via
solid state devices, to the use of computer technology.
One of the first recognizably modern embedded systems
was the Apollo Guidance Computer, developed byCharles Stark
Draper at the MIT Instrumentation Laboratory. At the project's
inception, the Apollo guidance computer was considered the riskiest
item in the Apollo project as it employed the then newly developed
monolithic integrated circuits to reduce the size and weight. An early
mass-produced embedded system was the Autonetics D-17 guidance
computer for theMinuteman missile, released in 1961. It was built
fromtransistor logic and had ahard disk for main memory. When the
Minuteman II went into production in 1966, the D-17 was replaced
with a new computer that was the first high-volume use of integrated
circuits.
2.1.2 Tools:
10
http://en.wikipedia.org/wiki/Programmable_controllershttp://en.wikipedia.org/wiki/Programmable_controllershttp://en.wikipedia.org/wiki/Electromechanicalhttp://en.wikipedia.org/wiki/Apollo_Guidance_Computerhttp://en.wikipedia.org/wiki/Charles_Stark_Draperhttp://en.wikipedia.org/wiki/Charles_Stark_Draperhttp://en.wikipedia.org/wiki/Minuteman_(missile)http://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Digital_circuithttp://en.wikipedia.org/wiki/Hard_diskhttp://en.wikipedia.org/wiki/Programmable_controllershttp://en.wikipedia.org/wiki/Programmable_controllershttp://en.wikipedia.org/wiki/Electromechanicalhttp://en.wikipedia.org/wiki/Apollo_Guidance_Computerhttp://en.wikipedia.org/wiki/Charles_Stark_Draperhttp://en.wikipedia.org/wiki/Charles_Stark_Draperhttp://en.wikipedia.org/wiki/Minuteman_(missile)http://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Digital_circuithttp://en.wikipedia.org/wiki/Hard_disk
-
8/18/2019 1.Three Phase Induction Motor Protection System
11/122
Embedded development makes up a small fraction of total
programming. There's also a large number of embedded architectures,
unlike the PC world where 1 instruction set rules, and the UNIX world
where there's only 3 or 4 major ones. This means that the tools are
more expensive. It also means that they're lowering featured, and less
developed. On a major embedded project, at some point you will
almost always find a compiler bug of some sort.
Debugging tools are another issue. Since you can't always
run general programs on your embedded processor, you can't always
run a debugger on it. This makes fixing your program difficult. Special
hardware such as JTAG ports can overcome this issue in part.
However, if you stop on a breakpoint when your system is controlling
real world hardware (such as a motor), permanent equipment damage
can occur. As a result, people doing embedded programming quickly
become masters at using serial IO channels and error message style
debugging.
2.1.3 Resources:
To save costs, embedded systems frequently have the
cheapest processors that can do the job. This means your programs
need to be written as efficiently as possible. When dealing with large
data sets, issues like memory cache misses that never matter in PC
programming can hurt you. Luckily, this won't happen too often- use
reasonably efficient algorithms to start, and optimize only when
necessary. Of course, normal profilers won't work well, due to the
same reason debuggers don't work well.
11
-
8/18/2019 1.Three Phase Induction Motor Protection System
12/122
Memory is also an issue. For the same cost savings
reasons, embedded systems usually have the least memory they can
get away with. That means their algorithms must be memory efficient
(unlike in PC programs, you will frequently sacrifice processor time for
memory, rather than the reverse). It also means you can't afford to
leak memory. Embedded applications generally use deterministic
memory techniques and avoid the default "new" and "malloc"
functions, so that leaks can be found and eliminated more easily.
Other resources programmers expect may not even exist. For example,
most embedded processors do not have hardware FPUs (Floating-Point
Processing Unit). These resources either need to be emulated in
software, or avoided altogether.
2.1.4 Real Time Issues:
Embedded systems frequently control hardware, and
must be able to respond to them in real time. Failure to do so could
cause inaccuracy in measurements, or even damage hardware such as
motors. This is made even more difficult by the lack of resources
available. Almost all embedded systems need to be able to prioritize
some tasks over others, and to be able to put off/skip low priority
tasks such as UI in favor of high priority tasks like hardware control.
2.2 Need For Embedded Systems:
The uses of embedded systems are virtually limitless,
because every day new products are introduced to the market that
utilizes embedded computers in novel ways. In recent years, hardware
such as microprocessors, microcontrollers, and FPGA chips have
become much cheaper. So when implementing a new form of control,
12
-
8/18/2019 1.Three Phase Induction Motor Protection System
13/122
it's wiser to just buy the generic chip and write your own custom
software for it. Producing a custom-made chip to handle a particular
task or set of tasks costs far more time and money. Many embedded
computers even come with extensive libraries, so that "writing your
own software" becomes a very trivial task indeed. From an
implementation viewpoint, there is a major difference between a
computer and an embedded system. Embedded systems are often
required to provide Real-Time response. The main elements that make
embedded systems unique are its reliability and ease in debugging.
2.2.1 Debugging:
Embedded debugging may be performed at different
levels, depending on the facilities available. From simplest to most
sophisticate they can be roughly grouped into the following areas:
• Interactive resident debugging, using the simple shell provided
by the embedded operating system (e.g. Forth and Basic)
• External debugging using logging or serial port output to trace
operation using either a monitor in flash or using a debug
server like the Remedy Debugger which even works for
heterogeneous multi core systems.
• An in-circuit debugger (ICD), a hardware device that connects to
the microprocessor via a JTAG or Nexus interface. This allows
the operation of the microprocessor to be controlled externally,
but is typically restricted to specific debugging capabilities in
the processor.
• An in-circuit emulator replaces the microprocessor with a
simulated equivalent, providing full control over all aspects of
the microprocessor.
13
-
8/18/2019 1.Three Phase Induction Motor Protection System
14/122
• A complete emulator provides a simulation of all aspects of the
hardware, allowing all of it to be controlled and modified and
allowing debugging on a normal PC.
• Unless restricted to external debugging, the programmer can
typically load and run software through the tools, view the code
running in the processor, and start or stop its operation. The
view of the code may be as assembly code or source-code.
Because an embedded system is often composed of a wide
variety of elements, the debugging strategy may vary. For instance,
debugging a software(and microprocessor) centric embedded system is
different from debugging an embedded system where most of the
processing is performed by peripherals (DSP, FPGA, co-processor). An
increasing number of embedded systems today use more than one
single processor core. A common problem with multi-core
development is the proper synchronization of software execution. In
such a case, the embedded system design may wish to check the data
traffic on the busses between the processor cores, which requires very
low-level debugging, at signal/bus level, with a logic analyzer, for
instance.
2.2.2 Reliability:
Embedded systems often reside in machines that are
expected to run continuously for years without errors and in some
cases recover by them if an error occurs. Therefore the software is
usually developed and tested more carefully than that for personal
computers, and unreliable mechanical moving parts such as disk
drives, switches or buttons are avoided.
14
-
8/18/2019 1.Three Phase Induction Motor Protection System
15/122
Specific reliability issues may include:
• The system cannot safely be shut down for repair, or it is too
inaccessible to repair. Examples include space systems,
undersea cables, navigational beacons, bore-hole systems, and
automobiles.
• The system must be kept running for safety reasons. "Limp
modes" are less tolerable. Often backup s is selected by an
operator. Examples include aircraft navigation, reactor control
systems, safety-critical chemical factory controls, train signals,
engines on single-engine aircraft.
• The system will lose large amounts of money when shut down:
Telephone switches, factory controls, bridge and elevator
controls, funds transfer and market making, automated sales
and service.
A variety of techniques are used, sometimes in combination, to
recover from errors—both software bugs such as memory leaks, and also soft
errors in the hardware:
• Watchdog timer that resets the computer unless the software
periodically notifies the watchdog
• Subsystems with redundant spares that can be switched over to
• software "limp modes" that provide partial function
• Designing with a Trusted Computing Base (TCB) architecture[6]
ensures a highly secure & reliable system environment
• An Embedded Hypervisor is able to provide secure
encapsulation for any subsystem component, so that a
compromised software component cannot interfere with other
subsystems, or privileged-level system software. This
encapsulation keeps faults from propagating from one
15
-
8/18/2019 1.Three Phase Induction Motor Protection System
16/122
subsystem to another, improving reliability. This may also allow
a subsystem to be automatically shut down and restarted on
fault detection.
• Immunity Aware Programming
2.3 Explanation of Embedded Systems:
2.3.1 Software Architecture:
There are several different types of software architecture in
common use.
• Simple Control Loop:
In this design, the software simply has a loop. The loop calls
subroutines, each of which manages a part of the hardware or
software.
• Interrupt Controlled System:
Some embedded systems are predominantly interrupt
controlled. This means that tasks performed by the system are
triggered by different kinds of events. An interrupt could be generated
for example by a timer in a predefined frequency, or by a serial port
controller receiving a byte. These kinds of systems are used if event
handlers need low latency and the event handlers are short and
simple.
Usually these kinds of systems run a simple task in a
main loop also, but this task is not very sensitive to unexpected
delays. Sometimes the interrupt handler will add longer tasks to a
queue structure. Later, after the interrupt handler has finished, these
16
-
8/18/2019 1.Three Phase Induction Motor Protection System
17/122
tasks are executed by the main loop. This method brings the system
close to a multitasking kernel with discrete processes.
• Cooperative Multitasking:
A non-preemptive multitasking system is very similar to
the simple control loop scheme, except that the loop is hidden in an
API. The programmer defines a series of tasks, and each task gets its
own environment to “run” in. When a task is idle, it calls an idle
routine, usually called “pause”, “wait”, “yield”, “nop” (stands for no
operation), etc.The advantages and disadvantages are very similar to
the control loop, except that adding new software is easier, by simply
writing a new task, or adding to the queue-interpreter.
• Primitive Multitasking:
In this type of system, a low-level piece of code switches
between tasks or threads based on a timer (connected to an interrupt).
This is the level at which the system is generally considered to have an
"operating system" kernel. Depending on how much functionality is
required, it introduces more or less of the complexities of managing
multiple tasks running conceptually in parallel.
As any code can potentially damage the data of another
task (except in larger systems using an MMU) programs must becarefully designed and tested, and access to shared data must be
controlled by some synchronization strategy, such as message queues,
semaphores or a non-blocking synchronization scheme.
Because of these complexities, it is common for
organizations to buy a real-time operating system, allowing the
application programmers to concentrate on device functionality rather
17
-
8/18/2019 1.Three Phase Induction Motor Protection System
18/122
than operating system services, at least for large systems; smaller
systems often cannot afford the overhead associated with a generic
real time system, due to limitations regarding memory size,
performance, and/or battery life.
• Microkernels And Exokernels:
A microkernel is a logical step up from a real-time OS.
The usual arrangement is that the operating system kernel allocates
memory and switches the CPU to different threads of execution. User
mode processes implement major functions such as file systems,
network interfaces, etc.
In general, microkernels succeed when the task switching
and inter task communication is fast, and fail when they are slow.
Exokernels communicate efficiently by normal subroutine calls. The
hardware and all the software in the system are available to, and
extensible by application programmers. Based on performance,
functionality, requirement the embedded systems are divided into
three categories:
2.3.2 Stand Alone Embedded System:
These systems takes the input in the form of electrical
signals from transducers or commands from human beings such as
pressing of a button etc.., process them and produces desired output.
This entire process of taking input, processing it and giving output is
done in standalone mode. Such embedded systems comes under
stand alone embedded systems
Eg: microwave oven, air conditioner etc..
2.3.3 Real-time embedded systems:
18
-
8/18/2019 1.Three Phase Induction Motor Protection System
19/122
-
8/18/2019 1.Three Phase Induction Motor Protection System
20/122
sending pictures, images, videos etc.., to another computer
with internet connection throughout anywhere in the world.
• Consider a web camera that is connected at the door lock.
Whenever a person comes near the door, it captures the
image of a person and sends to the desktop of your computer which is
connected to internet. This gives an alerting message with image on to
the desktop of your computer, and then you can open the door lock
just by clicking the mouse. Fig: 2.2 show the network communications
in embedded systems.
Fig 2.2: Network communication embedded systems
2.3.5 Different types of processing units:
The central processing unit (c.p.u) can be any one of the
following microprocessor, microcontroller, digital signal processing.
20
-
8/18/2019 1.Three Phase Induction Motor Protection System
21/122
• Among these Microcontroller is of low cost processor and one of
the main advantage of microcontrollers is, the components such
as memory, serial communication interfaces, analog to digital
converters etc.., all these are built on a single chip. The
numbers of external components that are connected to it are
very less according to the application.
• Microprocessors are more powerful than microcontrollers. They
are used in major applications with a number of tasking
requirements. But the microprocessor requires many external
components like memory, serial communication, hard disk,
input output ports etc.., so the power consumption is also very
high when compared to microcontrollers.
• Digital signal processing is used mainly for the applications that
particularly involved with processing of signals
2.4 APPLICATIONS OF EMBEDDED SYSTEMS:
2.4.1 Consumer applications:
At home we use a number of embedded systems which
include microwave oven, remote control, vcd players, dvd players,
camera etc….
Fig2.3: Automatic coffee makes equipment
21
-
8/18/2019 1.Three Phase Induction Motor Protection System
22/122
2.4.2 Office automation:
We use systems like fax machine, modem, printer etc…
Fig2.4: Fax machine Fig2.5:Printing machine
2.4.3. Industrial automation:
Today a lot of industries are using embedded systems for
process control. In industries we design the embedded systems to
perform a specific operation like monitoring temperature, pressure,
humidity ,voltage, current etc.., and basing on these monitored levels
we do control other devices, we can send information to a centralized
monitoring station.
Fig2.6: Robot
22
-
8/18/2019 1.Three Phase Induction Motor Protection System
23/122
In critical industries where human presence is avoided
there we can use robots which are programmed to do a specific
operation.
2.4.5 Computer networking:
Embedded systems are used as bridges routers etc..
Fig2.7: Computer networking
2.4.6 Tele communications:
Cell phones, web cameras etc.
23
-
8/18/2019 1.Three Phase Induction Motor Protection System
24/122
Fig2.8: Cell Phone Fig2.9: Web camera
CHAPTER 3: HARDWARE DESCRIPTION:
3.1 Introduction:
In this chapter the block diagram of the project and
design aspect of independent modules are considered. Block diagram
is shown in fig: 3.1:
24
-
8/18/2019 1.Three Phase Induction Motor Protection System
25/122
FIG 3.1: Block diagram of THREE PHASE INDUCTION MOTOR
PROTECTION SYSTEM”
The main blocks of this project are:
1.Micro controller (16F72)
2.Crystal oscillator
3.Reset
25
-
8/18/2019 1.Three Phase Induction Motor Protection System
26/122
4.Regulated power supply (RPS)
5.Led indicator
6.Voltage sensor
7.Optocoupler
8.Relay
9.LCD
3.2 Micro controller:
Fig: 3.2 Microcontrollers
Introduction
The PIC16F72 CMOS FLASH-based 8-bit microcontroller is
upward compatible withPIC16C72/72A and PIC16F872devices. It
features 200 ns instruction execution, self programming, an ICD, 2
Comparators, 5 channels of 8-bit Analog-to-Digital (A/D) converter, 2
capture/compare/PWM functions, a synchronous serial port that can
be configured as either 3-wire SPI or 2-wire I2C bus, a USART, and a
Parallel Slave Port.
High-Performance RISC CPU
26
-
8/18/2019 1.Three Phase Induction Motor Protection System
27/122
• High performance RISC CPU
• Only 35 single word instructions to learn
• All single cycle instructions except for program branches which are
two-cycle
• Operating speed: DC - 20 MHz clock input DC - 200 ns instruction
cycle
• 2K x 14 words of Program Memory
128 x 8 bytes of Data Memory (RAM)
• Pin out compatible to the PIC16C72/72A and PIC16F872
• Interrupt capability
• Eight level deep hardware stack
• Direct, Indirect and Relative Addressing modes
Peripheral Features
• Timer0: 8-bit timer/counter with 8-bit prescaler
• Timer1: 16-bit timer/counter with prescaler, can be incremented
during SLEEP via external crystal/clock
• Timer2: 8-bit timer/counter with 8-bit period register, prescaler and
postscaler
• Capture, Compare, PWM (CCP) module
- Capture is 16-bit, max resolution is 12.5 ns
- Compare is 16-bit, max resolution is 200 ns
27
-
8/18/2019 1.Three Phase Induction Motor Protection System
28/122
- PWM max resolution is 10-bit
• 8-bit, 5-channel Analog-to-Digital converter
• Synchronous Serial Port (SSP) with SPI (Master mode) and I2C
(Slave)
• Heat sink/Source Current:25 mA
• Brown-out detection circuitry for Brown-out Reset (BOR)
CMOS Technology:
• Low power, high speed CMOS FLASH technology
• Fully static design
• Wide operating voltage range: 2.0V to 5.5V
• Industrial temperature range
• Low power consumption:
- < 0.6 mA typical @ 3V, 4 MHz
- 20 μA typical @ 3V, 32 kHz
- < 1 μA typical standby current
Following are the major blocks of PIC Microcontroller.
Program memory (FLASH) is used for storing a written program.
Since memory made in FLASH technology can be programmed and
cleared more than once, it makes this microcontroller suitable for
device development.
28
-
8/18/2019 1.Three Phase Induction Motor Protection System
29/122
EEPROM - data memory that needs to be saved when there is no
supply.
It is usually used for storing important data that must not be lost if
power supply suddenly stops. For instance, one such data is an
assigned temperature in temperature regulators. If during a loss of
power supply this data was lost, we would have to make the
adjustment once again upon return of supply. Thus our device looses
on self-reliance.
RAM - Data memory used by a program during its execution.
In RAM are stored all inter-results or temporary data during run-time.
PORTS are physical connections between the microcontroller and the
outside world. PIC16F72 has 22 I/O.
FREE-RUN TIMER is an 8-bit register inside a microcontroller that
works independently of the program. On every fourth clock of the
oscillator it increments its value until it reaches the maximum (255),
and then it starts counting over again from zero. As we know the exact
timing between each two increments of the timer contents, timer can
be used for measuring time which is very useful with some devices.
CENTRAL PROCESSING UNIT has a role of connective element
between other blocks in the microcontroller. It coordinates the work of
other blocks and executes the user program.
29
-
8/18/2019 1.Three Phase Induction Motor Protection System
30/122
CISC, RISC
It has already been said that PIC16F72 has RISC architecture. This
term is often found in computer literature, and it needs to be
explained here in more detail. Harvard architecture is a newer concept
than von-Neumann. It rose out of the need to speed up the work of a
microcontroller. In Harvard architecture, data bus and address bus
are separate. Thus a greater flow of data is possible through the
central processing unit, and of course, a greater speed of work.
Separating a program from data memory makes it further possible for
instructions not to have to be 8-bit words. PIC16F72 uses 14 bits for
instructions, which allows for all instructions to be one-word
instructions. It is also typical for Harvard architecture to have fewer
instructions than von-Neumann's, and to have instructions usually
executed in one cycle.
Microcontrollers with Harvard architecture are also called "RISC
microcontrollers". RISC stands for Reduced Instruction Set Computer.
Microcontrollers with von-Neumann's architecture are called 'CISC
30
-
8/18/2019 1.Three Phase Induction Motor Protection System
31/122
microcontrollers'. Title CISC stands for Complex Instruction Set
Computer
Since PIC16F72 is a RISC microcontroller, that means that it has areduced set of instructions, more precisely 35 instructions. (Ex. Intel's
and Motorola's microcontrollers have over hundred instructions) All of
these instructions are executed in one cycle except for jump and
branch instructions. According to what its maker says, PIC16F72
usually reaches results of 2:1 in code compression and 4:1 in speed in
relation to other 8-bit microcontrollers in its class.
Crystal oscillator:
The crystal oscillator speed that can be connected to the PIC
microcontroller range from DC to 20Mhz. Using the CCS C compiler
normally 20Mhz oscillator will be used and the price is very cheap.
The 20 MHz crystal oscillator should be connected with about 22pF
capacitor. Please refer to my circuit schematic.
There are 5 input/output ports on PIC microcontroller namely
port A, port B, port C, port D and port E. Each port has different
function. Most of them can be used as I/O port.
Applications
PIC16F72 perfectly fits many uses, from automotive industries and
controlling home appliances to industrial instruments, remote
sensors, electrical door locks and safety devices. It is also ideal for
smart cards as well as for battery supplied devices because of its low
consumption.
31
-
8/18/2019 1.Three Phase Induction Motor Protection System
32/122
EEPROM memory makes it easier to apply microcontrollers to devices
where permanent storage of various parameters is needed (codes for
transmitters, motor speed, receiver frequencies, etc.). Low cost, low
consumption, easy handling and flexibility make PIC16F72 applicable
even in areas where microcontrollers had not previously been
considered (example: timer functions, interface replacement in larger
systems, coprocessor applications, etc.).
In System Programmability of this chip (along with using only two pins
in data transfer) makes possible the flexibility of a product, after
assembling and testing have been completed. This capability can be
used to create assembly-line production, to store calibration data
available only after final testing, or it can be used to improve programs
on finished products.
Clock / instruction cycle
Clock is microcontroller's main starter, and is obtained from an
external component called an "oscillator". If we want to compare a
microcontroller with a time clock, our "clock" would then be a ticking
sound we hear from the time clock. In that case, oscillator could be
compared to a spring that is wound so time clock can run. Also, force
used to wind the time clock can be compared to an electrical supply.
Clock from the oscillator enters a microcontroller via OSC1 pin where
internal circuit of a microcontroller divides the clock into four even
clocks Q1, Q2, Q3, and Q4 which do not overlap. These four clocks
make up one instruction cycle (also called machine cycle) during
which one instruction is executed.
32
-
8/18/2019 1.Three Phase Induction Motor Protection System
33/122
Execution of instruction starts by calling an instruction that is next in
string. Instruction is called from program memory on every Q1 and is
written in instruction register on Q4. Decoding and execution of
instruction are done between the next Q1 and Q4 cycles. On the
following diagram we can see the relationship between instruction
cycle and clock of the oscillator (OSC1) as well as that of internal
clocks Q1-Q4. Program counter (PC) holds information about the
address of the next instruction.
Pipelining
Instruction cycle consists of cycles Q1, Q2, Q3 and Q4. Cycles of
calling and executing instructions are connected in such a way that in
order to make a call, one instruction cycle is needed, and one more is
needed for decoding and execution. However, due to pipelining, each
instruction is effectively executed in one cycle. If instruction causes a
change on program counter, and PC doesn't point to the following but
to some other address (which can be the case with jumps or with
calling subprograms), two cycles are needed for executing an
instruction. This is so because instruction must be processed again,
but this time from the right address. Cycle of calling begins with Q1
33
-
8/18/2019 1.Three Phase Induction Motor Protection System
34/122
clock, by writing into instruction register (IR). Decoding and executing
begins with Q2, Q3 and Q4 clocks.
Pin description
PIC16F72 has a total of 28 pins. It is most frequently found in a DIP28
type of case but can also be found in SMD case which is smaller from
a DIP. DIP is an abbreviation for Dual In Package. SMD is an
abbreviation for Surface Mount Devices suggesting that holes for pinsto go through when mounting aren't necessary in soldering this type
of a component.
34
-
8/18/2019 1.Three Phase Induction Motor Protection System
35/122
Pins on PIC16F72 microcontroller have the following meaning:
There are 28 pins on PIC16F72. Most of them can be used as an IO
pin. Others are already for specific functions. These are the pin
functions.
1. MCLR – to reset the PIC
2. RA0 – port A pin 0
3. RA1 – port A pin 1
4. RA2 – port A pin 2
5. RA3 – port A pin 3
6. RA4 – port A pin 4
7. RA5 – port A pin 5
8. VSS – ground
9. OSC1 – connect to oscillator
10. OSC2 – connect to oscillator
35
-
8/18/2019 1.Three Phase Induction Motor Protection System
36/122
11. RC0 – port C pin 0 VDD – power supply
12. RC1 – port C pin 1
13. RC2 – port C pin 2
14. RC3 – port C pin 3
15. RC4 - port C pin 4
16. RC5 - port C pin 5
17. RC6 - port C pin 6
18. RC7 - port C pin 7
19. VSS - ground
20. VDD – power supply
21. RB0 - port B pin 0
22. RB1 - port B pin 1
23. RB2 - port B pin 2
24. RB3 - port B pin 3
25. RB4 - port B pin 4
26. RB5 - port B pin 5
27. RB6 - port B pin 6
28. RB7 - port B pin 7
By utilizing all of this pin so many application can be done such as:
1. LCD – connect to Port B pin.
2. LED – connect to any pin declared as output.
3. Relay and Motor - connect to any pin declared as output.
4. External EEPROM – connect to I2C interface pin – RC3 and RC4
(SCL and SDA)
5. LDR, Potentiometer and sensor – connect to analogue input pin
such as RA0.
6. GSM modem dial up modem – connect to RC6 and RC7 – the serial
communication interface using RS232 protocol.
36
-
8/18/2019 1.Three Phase Induction Motor Protection System
37/122
For more detail function for each specific pin please refer to the device
datasheet from Microchip.
Ports
Term "port" refers to a group of pins on a microcontroller which can be
accessed simultaneously, or on which we can set the desired
combination of zeros and ones, or read from them an existing status.
Physically, port is a register inside a microcontroller which is
connected by wires to the pins of a microcontroller. Ports represent
physical connection of Central Processing Unit with an outside world.
Microcontroller uses them in order to monitor or control other
components or devices. Due to functionality, some pins have twofold
roles like PA4/TOCKI for instance, which is in the same time the
fourth bit of port A and an external input for free-run counter.
Selection of one of these two pin functions is done in one of the
configuration registers. An illustration of this is the fifth bit T0CS in
OPTION register. By selecting one of the functions the other one is
disabled.
All port pins can be designated as input or output, according to the
needs of a device that's being developed. In order to define a pin as
input or output pin, the right combination of zeros and ones must be
written in TRIS register. If the appropriate bit of TRIS register contains
logical "1", then that pin is an input pin, and if the opposite is true,
it's an output pin. Every port has its proper TRIS register. Thus, port
A has TRISA, and port B has TRISB. Pin direction can be changed
during the course of work which is particularly fitting for one-line
communication where data flow constantly changes direction. PORTA
37
-
8/18/2019 1.Three Phase Induction Motor Protection System
38/122
and PORTB state registers are located in bank 0, while TRISA and
TRISB pin direction registers are located in bank 1.
PORTB and TRISB
PORTB have adjoined 8 pins. The appropriate register for data
direction is TRISB. Setting a bit in TRISB register defines the
corresponding port pin as input, and resetting a bit in TRISB register
defines the corresponding port pin as output.
Each PORTB pin has a weak internal pull-up resistor (resistor which
defines a line to logic one) which can be activated by resetting the
seventh bit RBPU in OPTION register. These 'pull-up' resistors are
automatically being turned off when port pin is configured as an
output. When a microcontroller is started, pull-ups are disabled.
38
-
8/18/2019 1.Three Phase Induction Motor Protection System
39/122
Four pins PORTB, RB7:RB4 can cause an interrupt which occurs
when their status changes from logical one into logical zero and
opposite. Only pins configured as input can cause this interrupt to
occur (if any RB7:RB4 pin is configured as an output, an interrupt
won't be generated at the change of status.) This interrupt option
along with internal pull-up resistors makes it easier to solve common
problems we find in practice like for instance that of matrix keyboard.
If rows on the keyboard are connected to these pins, each push on a
key will then cause an interrupt. A microcontroller will determine
which key is at hand while processing an interrupt It is not
recommended to refer to port B at the same time that interrupt is
being processed.
PORTA and TRISA
PORTA have 5 adjoining pins. The corresponding register for data
direction is TRISA at address 85h. Like with port B, setting a bit in
TRISA register defines also the corresponding port pin as input, and
clearing a bit in TRISA register defines the corresponding port pin as
output.
It is important to note that PORTA pin RA4 can be input only. On that
pin is also situated an external input for timer TMR0. Whether RA4
will be a standard input or an input for a counter depends on T0CS bit
(TMR0 Clock Source Select bit). This pin enables the timer TMR0 to
increment either from internal oscillator or via external impulses on
RA4/T0CKI pin.
Example shows how pins 0, 1, 2, 3, and 4 are designated input, and
pins 5, 6, and 7 outputs. After this, it is possible to read the pins RA2,
RA3, RA4, and to set logical zero or one to pins RA0 and RA1.
39
-
8/18/2019 1.Three Phase Induction Motor Protection System
40/122
Memory organization
PIC16F72 has two separate memory blocks, one for data and the other
for program. EEPROM memory with GPR and SFR registers in RAM
memory make up the data block, while FLASH memory makes up the
program block.
Program memory
Program memory has been carried out in FLASH technology which
makes it possible to program a microcontroller many times before it's
installed into a device, and even after its installment if eventual
changes in program or process parameters should occur. The size of
program memory is 1024 locations with 14 bits width where locations
zero and four are reserved for reset and interrupt vector.
Data memory
40
-
8/18/2019 1.Three Phase Induction Motor Protection System
41/122
Data memory consists of EEPROM and RAM memories. EEPROM
memory consists of 256 eight bit locations whose contents are not lost
during loosing of power supply. EEPROM is not directly addressable,
but is accessed indirectly through EEADR and EEDATA registers. As
EEPROM memory usually serves for storing important parameters (for
example, of a given temperature in temperature regulators) , there is a
strict procedure for writing in EEPROM which must be followed in
order to avoid accidental writing. RAM memory for data occupies
space on a memory map from location 0x0C to 0x4F which comes to
68 locations. Locations of RAM memory are also called GPR registers
which is an abbreviation for General Purpose Registers. GPR registers
can be accessed regardless of which bank is selected at the moment.
3.3 REGULATED POWER SUPPLY:
3.3.1 Introduction:
Power supply is a supply of electrical power. A device or
system that supplies electrical or other types of energyto an output
loador group of loads is called a power supply unit or PSU. The term
is most commonly applied to electrical energy supplies, less often to
mechanical ones, and rarely to others.
A power supply may include a power distribution system
as well as primary or secondary sources of energy such as
• Conversion of one form of electrical power to another desired
form and voltage, typically involving converting ACline voltage to a
well-regulated lower-voltage DCfor electronic devices. Low voltage,
low power DC power supply units are commonly integrated with
41
-
8/18/2019 1.Three Phase Induction Motor Protection System
42/122
the devices they supply, such as computers and household
electronics.
• Batteries.
• Chemical fuel cellsand other forms of energy storage systems.
• Solar power.
• Generators or alternators.
3.3.2 Block Diagram:
Fig 3.3.2 Regulated Power Supply
The basic circuit diagram of a regulated power supply (DC
O/P) with led connected as load is shown in fig: 3.3.3.
42
-
8/18/2019 1.Three Phase Induction Motor Protection System
43/122
Fig 3.3.3 Circuit diagram of Regulated Power Supply
with Led connection
The components mainly used in above figure are
• 230V AC MAINS
• TRANSFORMER
• BRIDGE RECTIFIER(DIODES)
• CAPACITOR
• VOLTAGE REGULATOR(IC 7805)
• RESISTOR
• LED(LIGHT EMITTING DIODE)
The detailed explanation of each and every component
mentioned above is as follows:
Step 1: Transformation: The process of transforming energy from
one device to another is called transformation. For transforming
energy we use transformers.
43
-
8/18/2019 1.Three Phase Induction Motor Protection System
44/122
Transformers:
A transformer is a device that transfers electrical
energy from one circuit to another through inductively
coupled conductors without changing its frequency. A
varying current in the first or primary winding creates a
varying magnetic flux in the transformer's core, and thus a
varying magnetic field through the secondary winding. This varying
magnetic field induces a varying electromotive force (EMF) or "voltage"
in the secondary winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current
will flow in the secondary winding and electrical energy will be
transferred from the primary circuit through the transformer to the
load. This field is made up from lines of force and has the same shapeas a bar magnet.
If the current is increased, the lines of force move
outwards from the coil. If the current is reduced, the lines of force
move inwards.
If another coil is placed adjacent to the first coil then, asthe field moves out or in, the moving lines of force will "cut" the turns
of the second coil. As it does this, a voltage is induced in the second
coil. With the 50 Hz AC mains supply, this will happen 50 times a
second. This is called MUTUAL INDUCTION and forms the basis of the
transformer.
44
-
8/18/2019 1.Three Phase Induction Motor Protection System
45/122
The input coil is called the PRIMARY WINDING; the
output coil is the SECONDARY WINDING. Fig: 3.3.4 shows step-down
transformer.
Fig 3.3.4: Step-Down Transformer
The voltage induced in the secondary is determined by the
TURNS RATIO.
For example, if the secondary has half the primary
turns; the secondary will have half the primary voltage.
Another example is if the primary has 5000 turns and the
secondary has 500 turns, then the turn’s ratio is 10:1.
If the primary voltage is 240 volts then the secondary
voltage will be x 10 smaller = 24 volts. Assuming a perfect
transformer, the power provided by the primary must equal the power
taken by a load on the secondary. If a 24-watt lamp is connected
across a 24 volt secondary, then the primary must supply 24 watts.
To aid magnetic coupling between primary and secondary,
the coils are wound on a metal CORE. Since the primary would
45
-
8/18/2019 1.Three Phase Induction Motor Protection System
46/122
induce power, called EDDY CURRENTS, into this core, the core is
LAMINATED. This means that it is made up from metal sheets
insulated from each other. Transformers to work at higher frequencies
have an iron dust core or no core at all.
Note that the transformer only works on AC, which has a
constantly changing current and moving field. DC has a steady
current and therefore a steady field and there would be no induction.
Some transformers have an electrostatic screen between
primary and secondary. This is to prevent some types of interference
being fed from the equipment down into the mains supply, or in the
other direction. Transformers are sometimes used for IMPEDANCE
MATCHING.
We can use the transformers as step up or step down.
Step Up transformer:
In case of step up transformer, primary windings are
every less compared to secondary winding. Because of having more
turns secondary winding accepts more energy, and it releases more
voltage at the output side.
Step down transformer:
Incase of step down transformer, Primary winding induces
more flux than the secondary winding, and secondary winding is
having less number of turns because of that it accepts less number of
flux, and releases less amount of voltage.
Battery power supply:
46
-
8/18/2019 1.Three Phase Induction Motor Protection System
47/122
A battery is a type of linear power supply that offers
benefits that traditional line-operated power supplies lack: mobility,
portability and reliability. A battery consists of multiple
electrochemical cells connected to provide the voltage desired. Fig:
3.3.5 shows Hi-Watt 9V battery
Fig 3.3.5: Hi-Watt 9V Battery
The most commonly useddry-cell battery is thecarbon-
zinc dry cell battery. Dry-cell batteries are made by stacking a carbon
plate, a layer of electrolyte paste, and a zinc plate alternately until the
desired total voltage is achieved. The most common dry-cell batteries
have one of the following voltages: 1.5, 3, 6, 9, 22.5, 45, and 90.
During the discharge of a carbon-zinc battery, the zinc metal is
converted to a zinc salt in the electrolyte, and magnesium dioxide is
reduced at the carbon electrode. These actions establish a voltage of
approximately 1.5 V.
Thelead-acid storage battery may be used. This battery is
rechargeable; it consists of lead and lead/dioxide electrodes which are
immersed in sulfuric acid. When fully charged, this type of battery has
a 2.06-2.14 V potential (A 12 voltcar battery uses 6 cells in series).
During discharge, the lead is converted to lead sulfate and the sulfuric
acid is converted to water. When the battery is charging, the lead
sulfate is converted back to lead and lead dioxide Anickel-
47
http://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Dry-cellhttp://en.wikipedia.org/wiki/Carbon-zinchttp://en.wikipedia.org/wiki/Carbon-zinchttp://en.wikipedia.org/wiki/Lead-acidhttp://en.wikipedia.org/wiki/Car_batteryhttp://en.wikipedia.org/wiki/Nickel-cadmiumhttp://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Dry-cellhttp://en.wikipedia.org/wiki/Carbon-zinchttp://en.wikipedia.org/wiki/Carbon-zinchttp://en.wikipedia.org/wiki/Lead-acidhttp://en.wikipedia.org/wiki/Car_batteryhttp://en.wikipedia.org/wiki/Nickel-cadmium
-
8/18/2019 1.Three Phase Induction Motor Protection System
48/122
-
8/18/2019 1.Three Phase Induction Motor Protection System
49/122
diodes, vacuum tube diodes, mercury arc valves, and other
components.
A device that it can perform the opposite function(converting DC to AC) is known as an inverter.
When only one diode is used to rectify AC (by blocking the
negative or positive portion of the waveform), the difference between
the term diode and the term rectifier is merely one of usage, i.e., the
term rectifier describes a diode that is being used to convert AC to DC.
Almost all rectifiers comprise a number of diodes in a specific
arrangement for more efficiently converting AC to DC than is possible
with only one diode. Before the development of silicon semiconductor
rectifiers, vacuum tube diodes and copper (I) oxide or selenium
rectifier stacks were used.
Bridge full wave rectifier:
The Bridge rectifier circuit is shown in fig:3.8, which
converts an ac voltage to dc voltage using both half cycles of the input
ac voltage. The Bridge rectifier circuit is shown in the figure. The
circuit has four diodes connected to form a bridge. The ac input
voltage is applied to the diagonally opposite ends of the bridge. The
load resistance is connected between the other two ends of the bridge.
For the positive half cycle of the input ac voltage,
diodes D1 and D3 conduct, whereas diodes D2 and D4 remain in the
OFF state. The conducting diodes will be in series with the load
resistance RL and hence the load current flows through RL.
49
-
8/18/2019 1.Three Phase Induction Motor Protection System
50/122
For the negative half cycle of the input ac voltage, diodes
D2 and D4 conduct whereas, D1 and D3 remain OFF. The conducting
diodes D2 and D4 will be in series with the load resistance RL and
hence the current flows through RL in the same direction as in the
previous half cycle. Thus a bi-directional wave is converted into a
unidirectional wave.
Input Output
Fig 3.3.7: Bridge rectifier: a full-wave rectifier using 4 diodes
DB107:
Now -a -days Bridge rectifier is available in IC with a
number of DB107. In our project we are using an IC in place of bridge
rectifier. The picture of DB 107 is shown in fig: 3.9.
Features:
• Good for automation insertion
• Surge overload rating - 30 amperes peak
50
-
8/18/2019 1.Three Phase Induction Motor Protection System
51/122
• Ideal for printed circuit board
• Reliable low cost construction utilizing molded
• Glass passivated device
• Polarity symbols molded on body
• Mounting position: Any
• Weight: 1.0 gram
Fig 3.3.8: DB107
Step 3: Filtration
The process of converting a pulsating direct current to a
pure direct current using filters is called as filtration.
Filters:
Electronic filters are electronic circuits, which perform
signal-processing functions, specifically to remove unwanted
frequency components from the signal, to enhance wanted ones.
Introduction to Capacitors:
51
-
8/18/2019 1.Three Phase Induction Motor Protection System
52/122
The Capacitor or sometimes referred to as a Condenser is
a passive device, and one which stores energy in the form of an
electrostatic field which produces a potential (static voltage) across its
plates. In its basic form a capacitor consists of two parallel conductive
plates that are not connected but are electrically separated either by
air or by an insulating material called the Dielectric. When a voltage is
applied to these plates, a current flows charging up the plates with
electrons giving one plate a positive charge and the other plate an
equal and opposite negative charge this flow of electrons to the plates
is known as the Charging Current and continues to flow until the
voltage across the plates (and hence the capacitor) is equal to the
applied voltage Vcc. At this point the capacitor is said to be fully
charged and this is illustrated below. The construction of capacitor
and an electrolytic capacitor are shown in figures 3.3.9 and 3.3.10
respectively.
52
-
8/18/2019 1.Three Phase Induction Motor Protection System
53/122
Fig 3.3.9:Construction Of a Capacitor Fig
3.3.10:Electrolytic Capaticor
Units of Capacitance:
Microfarad (μF) 1μF = 1/1,000,000 = 0.000001 = 10-6 F
Nanofarad (nF) 1nF = 1/1,000,000,000 = 0.000000001 = 10
-9
F
53
-
8/18/2019 1.Three Phase Induction Motor Protection System
54/122
-
8/18/2019 1.Three Phase Induction Motor Protection System
55/122
Where a capacitor is used to decouple a
circuit, the effect is to "smooth out
ripples". Any ripples, waves or pulses of
current are passed to ground while d.c.
Flows smoothly.
Step 4: Regulation
The process of converting a varying voltage to a constant
regulated voltage is called as regulation. For the process of regulation
we use voltage regulators.
Voltage Regulator:
A voltage regulator (also called a ‘regulator’) with only
three terminals appears to be a simple device, but it is in fact a very
complex integrated circuit. It converts a varying input voltage into a
constant ‘regulated’ output voltage. Voltage Regulators are available in
a variety of outputs like 5V, 6V, 9V, 12V and 15V. The LM78XX series
of voltage regulators are designed for positive input. For applications
requiring negative input, the LM79XX series is used. Using a pair of
‘voltage-divider’ resistors can increase the output voltage of a regulator
circuit.
It is not possible to obtain a voltage lower than the stated
rating. You cannot use a 12V regulator to make a 5V power supply.
Voltage regulators are very robust. These can withstand over-current
55
-
8/18/2019 1.Three Phase Induction Motor Protection System
56/122
draw due to short circuits and also over-heating. In both cases, the
regulator will cut off before any damage occurs. The only way to
destroy a regulator is to apply reverse voltage to its input. Reverse
polarity destroys the regulator almost instantly. Fig: 3.3.11 shows
voltage regulator.
Fig 3.3.11: Voltage Regulator
Resistors:
A resistor is a two-terminal electronic component that produces
a voltage across its terminals that is proportional to the electric
current passing through it in accordance with Ohm's law:
V =IR
Resistors are elements of electrical networks and electronic
circuits and are ubiquitous in most electronic equipment. Practical
resistors can be made of various compounds and films, as well as
resistance wire (wire made of a high-resistivity alloy, such as
nickel/chrome).
The primary characteristics of a resistor are the resistance, the
tolerance, maximum working voltage and the power rating. Other
characteristics include temperature coefficient, noise, and inductance.
56
-
8/18/2019 1.Three Phase Induction Motor Protection System
57/122
-
8/18/2019 1.Three Phase Induction Motor Protection System
58/122
Fig 3.3.12: Resistor Fig 3.3.13:
Color Bands In Resistor
3.4. LED:
A light-emitting diode (LED) is a semiconductor light
source. LEDs are used as indicator lamps in many devices, and are
increasingly used for lighting. Introduced as a practical electronic
component in 1962, early LEDs emitted low-intensity red light, but
58
-
8/18/2019 1.Three Phase Induction Motor Protection System
59/122
modern versions are available across the visible, ultraviolet and
infrared wavelengths, with very high brightness. The internal
structure and parts of a led are shown below.
Fig 3.4.1: Inside a LED Fig
3.4.2: Parts of a LED
Working:
59
-
8/18/2019 1.Three Phase Induction Motor Protection System
60/122
The structure of the LED light is completely different than
that of the light bulb. Amazingly, the LED has a simple and strong
structure. The light-emitting semiconductor material is what
determines the LED's color. The LED is based on the semiconductor
diode.
When a diode is forward biased (switched on), electrons
are able to recombine with holes within the device, releasing energy in
the form of photons. This effect is called electroluminescence and the
color of the light (corresponding to the energy of the photon) is
determined by the energy gap of the semiconductor. An LED is usually
small in area (less than 1 mm2), and integrated optical components
are used to shape its radiation pattern and assist in reflection. LEDs
present many advantages over incandescent light sources including
lower energy consumption, longer lifetime, improved robustness,
smaller size, faster switching, and greater durability and reliability.
However, they are relatively expensive and require more precise
current and heat management than traditional light sources. Current
LED products for general lighting are more expensive to buy than
fluorescent lamp sources of comparable output. They also enjoy use in
applications as diverse as replacements for traditional light sources in
automotive lighting (particularly indicators) and in traffic signals. The
compact size of LEDs has allowed new text and video displays and
sensors to be developed, while their high switching rates are useful in
advanced communications technology. The electrical symbol and
polarities of led are shown in fig: 3.4.3.
60
-
8/18/2019 1.Three Phase Induction Motor Protection System
61/122
Fig 3.4.3: Electrical Symbol & Polarities of LED
LED lights have a variety of advantages over other light sources:
• High-levels of brightness and intensity
• High-efficiency
• Low-voltage and current requirements
• Low radiated heat
• High reliability (resistant to shock and vibration)
• No UV Rays
• Long source life
•Can be easily controlled and programmed
Applications of LED fall into three major categories:
• Visual signal application where the light goes more or less
directly from the LED to the human eye, to convey a message or
meaning.
61
-
8/18/2019 1.Three Phase Induction Motor Protection System
62/122
• Illumination where LED light is reflected from object to give
visual response of these objects.
• Generate light for measuring and interacting with processes
that do not involve the human visual system.
3.5 VOLTAGE SENSOR:
In practice a voltage transformer can be used as a voltage sensor. The
voltage transformer must be connected across the transmission lines.
The primary of the transformer must be connected to the
transmission lines and the secondary must be given to the
microcontroller. A step down voltage transformer is used.
Illustration of a voltage sensor
Fig: Diagram of voltage sensor
In the project we have made use of a potentiometer in place of a
voltage sensor. Apotentiometer (colloquially known as a "pot") is a
three-terminal resistor with a sliding contact that forms an adjustable
voltage divider. It is a measuring device which measures the voltage or
current at the output by comparing it with the known input voltage.
Varying the input voltage is a difficult process and requires advanced
equipments. In the potentiometer the input is fixed at some maximum
and minimum value. By turning the notch of the potentiometer the
62
-
8/18/2019 1.Three Phase Induction Motor Protection System
63/122
output voltage is varied, whenever the output voltage exceeds the
bounds it indicates the occurrence of fault. After the fault is indicated
the microcontroller gives trip signals to the relay which in turn
operates the circuit breaker.
However in real time applications a potentiometer cannot be used, a
voltage transformer should be used.
3.6 OPTOCOUPLER
An optocoupler-isolated power supply is often the
safest and most practical way to go when it comes to performance and
protection. Here’s the basic on today’s LED/photo detector isolators
and what you need to know to apply them to your system. The junior
system designer often places the system’s power requirements at the
end of the list, and thus overlooks the importance of an isolated,
versus non-isolated AC/AC, AC/DC, DC/AC, or DC/DC converter.
True isolation (transformer at the input, optoisolator in the supply’s
feedback control loops) virtually removes any direct conductive path
between the power supply’s input stage and its output terminals/load.
That’s especially important in the high-power density applications that
are becoming more the rule than the exception, and for more
demanding system requirements
That often place power supplies in explosive or otherwise hazardous
environments.
The use of an optocoupler also acts to break ground
loops, and this functionality is valuable in eliminating common-mode
noise, especially for systems working at the higher operating voltages.
When different power supplies in a system are tied together, ground
63
-
8/18/2019 1.Three Phase Induction Motor Protection System
64/122
loop currents tend to be induced due to slight differences in ground
potential.
In addition, power supplies tend to see transient noise
in equipment that switches between various power states (today’s
optocouplers are able to withstand up to 40 kV/microsecond transient
common-mode voltage). Typical optocouplers for performing this so-
called galvanic isolation function—in essence to connect intrinsically
safe circuitry to circuits that pose a safety risk—comprise an LED, a
photo detector, and appropriate connecting circuitry in the supply’s
output-to-input feedback Loop. In general circuit operation, the
optocoupler, driven by the supply’s PWM, serves as the link to
maintain the supply’s desired output voltage When the output voltage
deviates either due to line and/or load changes, the supply’s error
amplifier attempts to compensate. It compares its input with a
reference voltage, and the error signal thus controls the output of the
PWM. In turn, the PWM directs the primary- side
Power MOSFET's via the optocoupler.
64
-
8/18/2019 1.Three Phase Induction Motor Protection System
65/122
The standards
Regulatory agencies such as UL in the United States,
CENELEC in Europe, CSA in Canada, and TIIS in Japan, set the
power level needed to make circuitry intrinsically safe. In essence, the
standards set the requirements for the galvanic isolation barrier
between the “safe” circuitry and the outside world. For best results,
choose optocouplers with additional reinforced insulation as suggested
by IEC EN-60747- 5-2. Reinforced insulation ensures protection from
electric shock as well as provides a failsafe mode. Fail-safe techniques
terminate system operation and leaves system processes and
components in a secure state when a failure occurs.
The input-voltage level usually defines the insulation
voltage rating, which typically ranges from 500 volts for some telecom
applications to 3500 volts for universal line-voltage capability. The
regulations you need to know about, and the specs you should study,include IEC60950, EN55022, and IEC 61000. IEC 61000 in particular
covers electromagnetic compatibility (EMC), and part 4 of that
document (IEC61000- 4-4) covers fast transient/burst Electrical Fast
Transient (EFT) testing discussed in part 4.4 addresses interference
simulated in inductively loaded switches. In this standard, the
modules will be subjected to the following test levels, depending on the
designed environment: Level 1 (Well protected); Level 2 (Protected);
Level 3 (Typical Industrial Environment); and Level 4 (Severe
Industrial Environment), where test voltage peaks at the power supply
ports are 0.5 kV (5kHz repetition rate), 1 kV (5kHz), 2 kV (5kHz), and 4
kV (2.5kHz), respectively.
65
-
8/18/2019 1.Three Phase Induction Motor Protection System
66/122
Simple Remote Reset Power On/Off
This is a simple schematic for a remote reset/power on/off
device
to use for controlling up to 4 lines via the parallel port.
Depending on the number of lines you require, the opto coupler
will be PC817, PC827 or PC847.
Or you could use the following schematic to drive up to 8 lines,
with the drawback that a reboot of the controlling machine will
probably reboot all your attached devices...
Applications
1.Computer terminals
2.System appliances, measuring instruments
3.Registers, copiers, automatic vending machines
4.Electric home appliances, such as fan heaters, etc.
5.Signal transmission between circuits of different potentials and
impedances
66
-
8/18/2019 1.Three Phase Induction Motor Protection System
67/122
3.7 Relay:
Arelay is an electrically operated switch. Many relays use an
electromagnet to operate a switching mechanism, but other operating
principles are also used. Relays find applications where it is necessary
to control a circuit by a low-power signal, or where several circuits
must be controlled by one signal. The first relays were used in long
distance telegraph circuits, repeating the signal coming in from one
circuit and re-transmitting it to another. Relays found extensive use in
telephone exchanges and early computers to perform logical
operations. A type of relay that can handle the high power required to
directly drive an electric motor is called a contactor. Solid-state relays
control power circuits with no moving parts, instead using a
semiconductor device triggered by light to perform switching. Relays
with calibrated operating characteristics and sometimes multiple
operating coils are used to protect electrical circuits from overload or
faults; in modern electric power systems these functions are
performed by digital instruments still called "protection relays".
3.8.1 Basic design and operation:
67
-
8/18/2019 1.Three Phase Induction Motor Protection System
68/122
1.Simple electromechanical relay
Small relay as used in electronics
A simple electromagnetic relay, such as the one taken from a car in
the first picture, is an adaptation of an electromagnet. It consists of a
coil of wire surrounding a soft iron core, an iron yoke, which provides
a low reluctance path for magnetic flux, a movable ironarmature, and
a set, or sets, of contacts; two in the relay pictured. The armature is
hinged to the yoke and mechanically linked to a moving contact or
contacts. It is held in place by a spring so that when the relay is de-
energized there is an air gap in the magnetic circuit. In this condition,
one of the two sets of contacts in the relay pictured is closed, and the
other set is open. Other relays may have more or fewer sets of contacts
depending on their function. The relay in the picture also has a wire
connecting the armature to the yoke. This ensures continuity of the
circuit between the moving contacts on the armature, and the circuit
track on the printed circuit board (PCB) via the yoke, which is
soldered to the PCB.
When an electric current is passed through the coil, the resulting
magnetic field attracts the armature and the consequent movement of
the movable contact or contacts either makes or breaks a connection
68
http://en.wikipedia.org/wiki/Armature_(electrical_engineering)http://en.wikipedia.org/wiki/Armature_(electrical_engineering)
-
8/18/2019 1.Three Phase Induction Motor Protection System
69/122
with a fixed contact. If the set of contacts was closed when the relay
was De-energized, then the movement opens the contacts and breaks
the connection, and vice versa if the contacts were open. When the
current to the coil is switched off, the armature is returned by a force,
approximately half as strong as the magnetic force, to its relaxed
position. Usually this force is provided by a spring, but gravity is also
used commonly in industrial motor starters. Most relays are
manufactured to operate quickly. In a low voltage application, this is
to reduce noise. In a high voltage or high current application, this is to
reduce arcing.
If the coil is energized with DC, a diode is frequently installed across
the coil, to dissipate the energy from the collapsing magnetic field at
deactivation, which would otherwise generate a voltage spike
dangerous to circuit components. Some automotive relays already
include a diode inside the relay case. Alternatively a contact protection
network, consisting of a capacitor and resistor in series, may absorb
the surge. If the coil is designed to be energized with AC, a small
copper ring can be crimped to the end of the solenoid. This "shading
ring" creates a small out-of-phase current, which increases the
minimum pull on the armature during the AC cycle.
By analogy with the functions of the original electromagnetic device, asolid-state relay is made with a thyristor or other solid-state switching
device. To achieve electrical isolation an opt coupler can be used
which is a light-emitting diode (LED) coupled with a photo transistor.
69
-
8/18/2019 1.Three Phase Induction Motor Protection System
70/122
3.8.2 Types of Relays:
2. Latching relay
Latching relay, dust cover removed, showing pawl and ratchet
mechanism. The ratchet operates a cam, which raises and lowers the
moving contact arm, seen edge-on just below it. The moving and fixed
contacts are visible at the left side of the image.
Alatching relay has two relaxed states (bi stable). These are also
called "impulse", "keep", or "stay" relays. When the current is switched
off, the relay remains in its last state. This is achieved with a solenoid
operating a ratchet and cam mechanism, or by having two opposing
coils with an over-center spring or permanent magnet to hold the
armature and contacts in position while the coil is relaxed, or with a
remnant core. In the ratchet and cam example, the first pulse to the
coil turns the relay on and the second pulse turns it off. In the two
coil example, a pulse to one coil turns the relay on and a pulse to the
opposite coil turns the relay off. This type of relay has the advantage
that it consumes power only for an instant, while it is being switched,
and it retains its last setting across a power outage. A remnant core
latching relay requires a current pulse of opposite polarity to make it
change state.
70
-
8/18/2019 1.Three Phase Induction Motor Protection System
71/122
3. Reed relay
Areed relay has a set of contacts inside a vacuum or inert gas filled
glass tube, which protects the contacts against atmospheric corrosion.
The contacts are closed by a magnetic field generated when current
passes through a coil around the glass tube. Reed relays are capable
of faster switching speeds than larger types of relays, but have low
switch current and voltage ratings.
4. Mercury-wetted relay
Amercury-wetted reed relay is a form of reed relay in which the
contacts are wetted with mercury. Such relays are used to switch low-
voltage signals (one volt or less) because of their low contact
resistance, or for high-speed counting and timing applications where
the mercury eliminates contact bounce. Mercury wetted relays are
position-sensitive and must be mounted vertically to work properly.
Because of the toxicity and expense of liquid mercury, these relays are
rarely specified for new equipment. See also mercury switch.
5. Polarized relay
A polarized relay placed the armature between the poles of a
permanent magnet to increase sensitivity. Polarized relays were used
in middle 20th Century telephone exchanges to detect faint pulses and
71
http://en.wikipedia.org/wiki/File:Reedrelay.jpg
-
8/18/2019 1.Three Phase Induction Motor Protection System
72/122
correct telegraphic distortion. The poles were on screws, so a
technician could first adjust them for maximum sensitivity and then
apply a bias spring to set the critical current that would operate the
relay.
6. Machine tool relay
Amachine tool relay is a type standardized for industrial control of
machine tools, transfer machines, and other sequential control. They
are characterized by a large number of contacts (sometimes
extendable in the field) which are easily converted from normally-open
to normally-closed status, easily replaceable coils, and a form factor
that allows compactly installing many relays in a control panel.
Although such relays once were the backbone of automation in such
industries as automobile assembly, the programmable logic controller
(PLC) mostly displaced the machine tool relay from sequential control
applications.
7. Contactor relay
Acontactor is a very heavy-duty relay used for switching electric
motors and lighting loads. Continuous current ratings for common
contactors range from 10 amps to several hundred amps. High-
current contacts are made with alloys containing silver. The
unavoidable arcing causes the contacts to oxidize; however, silver
oxide is still a good conductor. Such devices are often used for motor
starters. A motor starter is a contactor with overload protection
devices attached. The overload sensing devices are a form of heat
operated relay where a coil heats a bi-metal strip, or where a solder
pot melts, releasing a spring to operate auxiliary contacts. These
72
-
8/18/2019 1.Three Phase Induction Motor Protection System
73/122
auxiliary contacts are in series with the coil. If the overload senses
excess current in the load, the coil is de-energized. Contactor relays
can be extremely loud to operate, making them unfit for use where
noise is a chief concern.
8. Solid-state relay
Solid state relay, which has no moving parts
25 A or 40 A solid state contactors
Asolid state relay (SSR) is a solid state electronic component that
provides a similar function to an electromechanical relay but does not
have any moving components, increasing long-term reliability. With
early SSR's, the tradeoff came from the fact that every transistor has a
small voltage drop across it. This voltage drop limited the amount of
current a given SSR could handle. As transistors improved, higher
current SSR's, able to handle 100 to 1,200 Amperes, have become
73
http://en.wikipedia.org/wiki/File:Solid_state_relay.jpg
-
8/18/2019 1.Three Phase Induction Motor Protection System
74/122
commercially available. Compared to electromagnetic relays, they may
be falsely triggered by transients.
9. Solid state contactor relay
A solid state contactor is a very heavy-duty solid state relay,
including the necessary heat sink, used for switching electric heaters,
small electric motors and lighting loads; where frequent on/off cycles
are required. There are no moving parts to wear out and there is no
contact bounce due to vibration. They are activated by AC control
signals or DC control signals from Programmable logic controller
(PLCs), PCs, Transistor-transistor logic (TTL) sources, or other
microprocessor and microcontroller controls.
10. Buchholz relay
ABuchholz relay is a safety device sensing the accumulation of gas in
large oil-filled transformers; this will Display on slow accumulation of
gas or shut down the transformer if gas is produced rapidly in the
transformer oil.
11. Forced-guided contacts relay
A forced-guided contacts relay has relay contacts that are
mechanically linked together, so that when the relay coil is energized
or de-energized, all of the linked contacts move together. If one set of
contacts in the relay becomes immobilized, no other contact of the
same relay will be able to move. The function of forced-guided contacts
is to enable the safety circuit to check the status of the relay. Forced-
guided contacts are also known as "positive-guided contacts", "captive
contacts", "locked contacts", or "safety relays".
74
-
8/18/2019 1.Three Phase Induction Motor Protection System
75/122
12. Overload protection relay
Electric motors need over current protection to prevent damage from
over-loading the motor, or to protect against short circuits in
connecting cables or internal faults in the motor windings. One type of
electric